Roational Inertia ?

Ok, so I read the articles on Rotational mass, sprung and unsprung weight. But one thing I didn't get, why no Twin Turbo Supra's rolling on 15's? The way I understand, the smaller the wheel, the less rotating mass, the faster it goes. Like the ice skater thing. Yet Supra on 18's is a must. Help me out here.

everything is a compromise. bigger brakes will help to stop a vehicle with bigger wheels that make for a larger rolling diameter and more rotational mass. the car company's making these cars really know what they're doing. the size of the wheel on their cars are carefully calculated by engineers considering manufactoring costs vs performance vs economy.

supra's don't run on 15's because they need bigger wheels to help put the additional power they're putting down. some grand prix cars run on 18's and 19's, simply because the brakes they need to stop the car and tires they need to hold the car have to be 8,9 and even 10 inches wide.

you have to look at the entire setup, and remember that our little honda's weigh under 3k lbs and 15 x 7's are more than good enough for almost all civics.